Data Management Plan

Original Data Product: Hydroflattened Digital Elevation Model (DEM) data covering the Nisqually River Basin 2020 project area.

Original Geographic Extent: This dataset and derived products encompass an area covering approximately 13,189 acres of Western Washington.

Original Dataset Description: Lidar flight line swaths were processed to create 85 classified LAS 1.4 files delineated in 1,000m x 1,000m tiles. Each LAS file contains lidar point information, which has been calibrated, controlled, and classified. Class 2 (ground) lidar points in conjunction with the hydro breaklines were used to create 85 1.0 meter hydro-flattened Raster DEMs delineated in 1,000m x 1,000m tiles. Non-Vegetated Vertical Accuracy (NVA) was assessed using 22 check points located on bare earth in clear, unobstructed areas. Vegetated Vertical Accuracy (VVA) was assessed using 14 check points in tall grass, forest, and shrubland landcover types. Additional products include classified LAS files, intensity images, topobathymetric bare earth DEMs, highest hit surface models, and 3D breaklines of rivers and lakes within the study area.

Ground Condition: Ground condition was free of snow and acquisition occurred free of smoke, fog and cloud cover.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the USGS GeoTIFF files hosted by USGS on Amazon Web Services.

Lineage Statement:
The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.

Process Steps:

• 2021-03-30 00:00:00 - Lidar Pre-Processing:1. Review flight lines and data to ensure complete coverage of the study area and positional accuracy of the laser points.2. Resolve kinematic corrections for aircraft position data using kinematic aircraft GPS and static ground GPS data.3. Develop a smoothed best estimate of trajectory (SBET) file that blends post-processed aircraft position with sensor head position and attitude recorded throughout the survey.4. Calculate laser point position by associating SBET position to each laser point return time, scan angle, intensity, etc. Create raw laser point cloud data for the entire survey in *.las format. Convert data to orthometric elevations by applying a Geoid 18 correction.5. Apply refraction correct to bathymetric returns by flightline.6. Import raw laser points into manageable blocks to perform manual relative accuracy calibration and filter erroneous points. Classify ground points for individual flight lines.7. Using ground classified points per each flight line, test the relative accuracy. Perform automated line-to-line calibrations for system attitude parameters (pitch, roll, heading), mirror flex (scale) and GPS/IMU drift. Calculate calibrations on ground classified points from paired flight lines and apply results to all points in a flight line. Use every flight line for relative accuracy calibration.8. Adjust the point cloud by comparing ground classified points to supplemental ground control points.
• 2021-03-30 00:00:00 - Lidar Post-Processing:1. Classify data to ground and other client designated classifications using proprietary classification algorithms.2. Manually QC data classification3. After completion of classification and final QC approval, calculate final NVA, VVA, and density information for the project using ground control quality check points.
• 2021-03-30 00:00:00 - Breaklines: Water boundary polygons were developed using an algorithm which weights lidar-derived slopes, intensities, and return densities to detect the water's edge. The water's edge was then manually reviewed and edited as necessary.
• 2021-03-30 00:00:00 - Bathymetric Coverage Shape: Insufficiently mapped areas were identified by triangulating bathymetric bottom points with an edge length maximum of 4.56 meters. This shape was used to clip the final topobathymetric DEMs to avoid interpolation over areas lacking bathymetric returns.
• 2024-12-03 00:00:00 - The NOAA Office for Coastal Management (OCM) created references to the USGS GeoTIFF files that were ingested into the NOAA Digital Coast Data Access Viewer (DAV). No changes were made to the data. The DAV will access the raster data as it resides on Amazon Web Services (AWS). This is the location of the GeoTIFF files that are being accessed: https://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/Elevation/OPR/Projects/WA_Nisqually_TopoBathy_2020_D20/WA_Nisqually_TopoBathy_1_2020/TIFF/

Data is available online for bulk and custom downloads.

Data is backed up to tape and to cloud storage.